The Jaco2 service robot was designed and engineered by Kinova Robotics. Here, the robot shows how well it handles fragile household items. Photo courtesy of Kinova Robotics
Service robots for the disabled must be reliable, safe and easy to use. The right motion system components are essential for these highly specific applications.
Unlike industrial robots for manufacturing, service robots come with their own specification requirements aimed specifically at the end user, and the most discriminating user at that—a human being. That’s why designing and manufacturing service robots takes a particular set of skills and engineering expertise. For example, when Canada-based Kinova Robotics creates designs for this market, the design team brings years of experience in the field. And although they’ve modified the robots over the years, as new products and systems become readily available, they can produce higher quality and more useable products. Using the latest technologies allows the designers to continue to advance offerings to the public.
The company’s Jaco2 Robotic Arm provides a lightweight, quiet and easily controlled device to the service industry. The robotic arm moves around 6° of freedom through the use of six flat motors designed and manufactured by maxon precision motors.
The arm was designed using six joints from a shoulder-type joint through to a functional wrist joint. The robot can manipulate a maximum payload of 1.5 kg at full extension, as well as a 2.5 kg payload at a mid-range extension. Both of these payloads are adequate for the needs of most disabled people in the process of living a normal life. The robotic arm device itself weighs only 5.3 kg, which was an important specification for it to mount to a wheelchair without tipping it over.
Because the first three joints must handle the highest torque for movement of the extended arm as well as for lifting items a user needs, the design team chose to use maxon’s EC 45 flat brushless dc motors. These motors deliver a maximum continuous torque to 134 mNm (19 oz-in.) in a small, compact 70 W package. And since the Jaco2 needed to fit inside the robotic arm itself, there had to be less heat generated through motor operation—a huge benefit of the flat motors. Although the motors can operate at very high speeds, that was not a necessary requirement for the application. For the robotic arm to be manipulated efficiently, the device only needed to move at a speed of 20 cm per second, which translates to about 8 rpm maximum for the actuators’ outputs (about 1100 rpm for the motors).
第二三个关节Jaco2手臂也EC 45 flat motors, but are 30 W versions. Again, they were chosen to help keep heat dissipation at a minimum, since the motors were mounted inside the arm itself. Further, the flat motors were necessary because of the compact space allocated to the robot joints. The motor efficiencies were a critical point in selecting the EC series for the application. Plus, according to one member of the engineering team, maxon was open to slight customizations, which allowed the team to fit the motors to the application perfectly. Through the use of slip rings that were designed and manufactured in-house, each axis on the arm has infinite rotational capability.
用于臂的齿轮装载谐波驱动器转换为1：136的接头中的大型致动器的1：136的比率，在接头中的大致动器中的大型致动器的1：160比，1：110比在关节四个中的小型致动器的比率，五，六。
The Jaco2 easily mounts to a wheelchair and stays out of the way.
The Jaco2 Service Robot uses three EC 32, 15 W motors to operate the finger of the robot. Kinova engineers provided an in-house design for the lead screw mechanisms incorporated inside the fingers. The linear actuators had to be small due to the limited space available. The actuators were designed in-house because the company’s engineering team found that it was less expensive to design the lead screws they needed than to buy them off the shelf from another vendor. Although the flat motors have some minor degree of cogging, that did not affect the accuracy or other operations of the robot that would be critical to the user. Quiet operation of the motors only added to their overall appeal for the application, especially because of the human-robot interaction. The company wanted the device to be as transparent as possible to a user.
All the motors in the arm are daisy chained using a single cable that runs through the system. The tight form factor dictated the size and type of motor the design team could use. The Jaco2 uses 18 to 29 Vdc for operation at 25 W nominal power (100 W peak power). Control of the arm is performed through an RS485 (internal) and CANBUS (external) protocol. The system comes with two expansion card connectors for future use.
The controller features redundant security on each actuator/finger, redundant error check in actuators and control system, position and error calculation performed every 0.01 seconds, Cartesian and angular trajectory control, and force and torque control options.
Maxon’s EC series flat motors are highly efficient and compact. Photo couresty of maxon precision motors, inc.
每个Jaco2机器人手臂都通过用户的轮椅控制或通过用户友好的操纵杆来控制，这为残疾人的人机互动提供了精确度。系统所需的所有软件是由Kinova机器人工程团队编写的，以便Jaco2的操作符合他们的内部规格和目标。该软件在Windows，Linux Ubuntu和ROS上运行，并使用C＃和C ++编写。
maxon precision motors, inc.
www.maxonmotorusa.com
Filed Under:TECHNOLOGIES + PRODUCTS,The Robot Report,Slip rings + rotary unions
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